Signal Chain Design Guide - Microchip Technology

1 & Interface SolutionsFall 2012 Signal Chain Design GuideDevices For Use With SensorsDesign ideas in this Guide use the following devices. A complete device list and corresponding data sheets for these products can be found at AmplifiersInstrumentation AmplifiersComparatorsAnalog-to-Digital ConvertersDigital PotentiometersDigital-to-Analog ConvertersVoltage ReferencesTemperature SensorsMCP6 XXMCP6 XXXMCP6 VXXMCP6 HXXMCP6 NXXMCP654 XMCP656 XMCP65R4 XMCP30 XXMCP32 XXMCP33 XXMCP34 XXMCP35 XXMCP39 XXMCP40 XXMCP40D1 XMCP41 XXMCP42 XXMCP43 XXMCP45 XXMCP46 XXMCP41 XXXMCP42 XXXMCP47 XXMCP48 XXMCP49 XXMCP47DA1 MCP47A1TC132 XMCP1525 MCP1541 MCP98 XXMCP9700/AMCP9701/A2 Signal Chain Design GuideSignal Chain OverviewTypical sensor Signal Chain Control LoopDigital DomainAnalog DomainDriver(MOSFET)Op AmpDAC/PWMA ctuatorsMotors, Valves,Relays, Switches,Speakers, Horns,LEDsADC/V-to-FreqAmpSensorsFilterR eferenceVoltageMUXPIC MCU or dsPIC DSCI ndicator(LCD, LED)DigitalPotentiometerTypical sensor applications involve the monitoring of sensor parameters and controlling of actuators.

2 The sensor Signal Chain , as shown below, consists of analog and digital domains. Typical sensors output very low amplitude analog signals. These weak analog signals are amplified and filtered, and converted to digital values using op amps, analog-to-digital or voltage-to-frequency converters, and are processed at the MCU. The analog sensor output typically needs proper Signal conditioning before it gets converted to a digital MCU controls the actuators and maintains the operation of the sensor Signal conditioning circuits based on the condition of the Signal detection. In the digital to analog feedback path, the digital-to-analog converter (DAC), digital potentiometer and Pulse-Width-Modulator (PWM) devices are most commonly used. The MOSFET driver is commonly used for the interface between the feedback circuit and actuators such as motors and valves. Microchip offers a large portfolio of devices for Signal Chain Chain Design GuideMany system applications require the measurement of a physical or electrical condition, or the presence or absence of a known physical, electrical or chemical quantity.

3 Analog sensors are typically used to indicate the magnitude or change in the environmental condition, by reacting to the condition and generating a change in an electrical property as a phenomena that are measured are: Electrical Signal and properties Magnetic Signal and properties Temperature Humidity Force, weight, torque and pressure Motion and vibration Flow Fluid level and volume Light and infrared Chemistry/gasSummary Of Common Physical Conditions and Related sensor TypesPhenomenaSensorElectrical OutputMagneticHall EffectVoltageMagneto-ResistiveResistance TemperatureThermocoupleVoltageRTDR esistanceThermistorResistanceICVoltageIn fraredCurrentHumidityCapacitiveCapacitan ceInfraredCurrentForce, Weight, Torque, PressureStrain GaugeResistance/VoltageLoad CellResistancePiezoelectricVoltage or ChargeMechanical TransducerResistance, Voltage, CapacitanceMotion and VibrationLVDTAC VoltagePiezoelectricVoltage or ChargeMicrophoneVoltageUltrosonicVoltage , Resistive, CurrentAccelerometerVoltageFlowMagnetic FlowmeterVoltageMass FlowmeterResistance/VoltageUltrasound/Do pplerFrequencyHot-wire AnemometerResistanceMechanical Transducer (turbine)

4 VoltageFluid Level and VolumeUltrasoundTime DelayMechanical TransducerResistance/VoltageCapacitorCap acitanceSwitchOn/OffThermalVoltageTouchC apacitanceVoltageInductanceCurrentResist anceFrequencyProximityCapacitanceVoltage , FrequencyInductanceCurrent, FrequencyResistanceVoltage, CurrentLightPhotodiodeCurrentChemicalpH ElectrodeVoltageSolution ConductivityResistance/CurrentCO SensorVoltage or ChargePhotodiode (turbidity, colorimeter)CurrentIon SensorCurrentSensor OverviewThere are sensors that respond to these phenomena by producing the following electrical properties: Voltage Current Resistance Capacitance ChargeThis electrical property is then conditioned by an analog circuit before being driven to a digital circuit. In this way, the environmental condition can be measured and the system can make decisions based on the table below provides an overview of typical phenomena, the type of sensor commonly used to measure the phenomena and electrical output of the additional information, please refer to Application Note Chain Design GuideOperational Amplifiers (Op Amps) Microchip Technology offers a broad portfolio of op amp families built on advanced CMOS Technology .

5 These families are offered in single, dual and quad configurations, which are available in space saving op amp families include devices with Quiescent Current (Iq) per amplifier between A and 6 mA, with a Gain Bandwidth Product (GBWP) between 9 kHz and 60 MHz, respectively. The op amp with lowest supply voltage (Vdd) operates between and , while the op amp with highest Vdd operates between and op amp families fall into the following categories: General Purpose, Precision (including EPROM Trimmed and mCal Technology ) and Amplifiers (INA) Microchip has expanded its portfolio of amplifiers with the industry s first instrumentation amplifier featuring mCal Technology . The MCP6N11 features rail-to-rail input and output, operation and low offset/offset offers a broad portfolio of low-power and high-speed comparators. The MCP6541 and MCP6561 family of comparators provide ultra low power, 600 nA typical, and higher speed with 40 ns propagation delay, respectively.

6 Both families of comparators are available with single, dual and quad, as well as with push-pull and open-drain output options (for MCP6546 and MCP6566).The MCP65R41 and MCP65R46 family of push-pull and open-drain output comparators are offered with integrated reference voltages of and receptively. This family provides 1% typical tolerance while consuming A and high speed with 4 s propagation delay. These comparators operate with a single-supply voltage as low as to , which makes them ideal for low cost and/or battery powered OverviewsProgrammable Gain Amplifier (PGA)The MCP6S21/2/6/8 and MCP6S91/2/3 PGA families give the designer digital control over an amplifier using a serial interface (SPI bus). An input analog multiplexer with 1, 2, 6 or 8 inputs can be set to the desired input Signal . The gain can be set to one of eight non-inverting gains: + 1, 2, 4, 5, 8, 10, 16 and 32 V/V. In addition, a software shutdown mode offers significant power savings for portable embedded designs.

7 This is all achieved in one simple integrated part that allows for considerably greater bandwidth, while maintaining a low supply current. Systems with multiple sensors are significantly MCP6G01 family are analog Selectable Gain Amplifiers (SGA). The Gain Select input pin(s) set a gain of + 1 V/V, +10 V/V and + 50 V/V. The Chip Select pin on the MCP6G03 puts it into shutdown to conserve Converters (ADC) Microchip offers a broad portfolio of high-precision Delta-Sigma, SAR and Dual Slope A/D Converters. The MCP3550/1/3 Delta-Sigma ADCs offer up to 22-bit resolution with only 120 A typical current consumption in a small 8-pin MSOP package. The MCP3421 is a single channel 18-bit Delta-Sigma ADC and is available in a small 6-pin SOT-23 package. It includes a voltage reference and PGA. The user can select the conversion resolution up to 18 bits. The MCP3422/3 and the MCP3424 are two channel and four channel versions, respectively, of the MCP3421 device. The MCP300X (10-bit), MCP320X (12-bit) and MCP330X (13-bit) SAR ADCs combine high performance and low power consumption in a small package, making them ideal for embedded control applications.

8 The MCP3911 analog front end offer two simultaneously sampled 24-bit Delta-Sigma ADCs making it ideal for voltage and current measurement, and other data acquisition Analog-to-Digital Converter Design Guide ( Microchip Document No. 21841) shows various application examples of the ADC also offers many high accuracy energy metering devices which are based on the Delta-Sigma ADC cores. The Complete Utility Metering Solution Guide ( Microchip Document No: 24930) offers detailed solutions for metering Chain Design GuideVoltage ReferencesMicrochip offers the MCP15XX family of low power and low dropout precision Voltage References. The family includes the MCP1525 with an output voltage of and the MCP1541 with an output voltage of Microchip s voltage references are offered in SOT23-3 and TO-92 SensorsMicrochip offers a broad portfolio of thermal management products, including Logic Output, Voltage Output and Serial Output temperature sensors. These products allow the system designer to implement the device that best meets the application requirements.

9 Key features include high accuracy (such as MCP9808, with C maximum accuracy from 20 C to 100 C), low power, extended temperature range and small packages. In addition, other Microchip products can be used to support Thermocouple, RTD and Thermistor PotentiometersMicrochip s family of digital potentiometers offer a wide range of options. These devices support the 6-bit through 8-bit applications. Offering both volatile and non-volatile options, with digital interfaces from the simple Up/Down interface to the standard SPI and I2C interfaces. These devices are offered in small packages such as 6-lead SC70 and 8-lead DFN for the single potentiometer devices, 14-lead TSSOP and 16-lead QFN packages for the dual potentiometer devices, and 20-lead TSSOP and QFN packages for the quad potentiometer devices. Non-volatile devices offer a Wiperlock Technology feature, while volatile devices will operate down to Resistances are offered from k to 100 k . Over 50 device configurations are currently Digital Potentiometer Design Guide ( Microchip Document No.)

10 22017), shows various application examples of the digital potentiometer OverviewsDigital-to-Analog Converters (DAC) Microchip s family of Digital-to-Analog Converters (DACs) offer a wide range of options. These devices support the 6-bit through 12-bit applications. Offering both volatile and non-volatile options, and standard SPI and I2C digital interfaces. These devices are offered in small packages such as 6-lead SC70, SOT-23 and DFN (2 2) for the single output devices and 10-pin MSOP for quad output devices. Some versions support selecting either the device Vdd, the external voltage reference or an internally generated voltage reference source from the DAC circuitry. Devices with nonvolatile memory (EEPROM) allow the device to retain the programmed output code and DAC state through power down DAC devices provide high accuracy and low noise and are ideal for industrial applications where calibration or compensation of signals (such as temperature, pressure or humidity) is required.